Whether because of burns, age-related baldness or other diseases, both men and women are vulnerable to losing significant quantities of hair. There are limited options available for helping them grow it back, but scientists are trying to unlock solutions.

A new study, published Monday in the journal Proceedings of the National Academy of Sciences, offers fresh potential for restoring hair, using a person's own cells. Study authors demonstrated their technique on the backs of mice, but they've genetically confirmed that the hairs themselves are human.

"Everything was done in human cells, both the donors and the recipients. In most of the work that’s been done up to now it’s a hybrid – the hairs are usually part rodent and part human," said Angela Christiano, professor of dermatology at Columbia University Medical Center, one of the senior authors of the new study. "So having an assay that’s all human is actually a big thing."

Who benefits?

Hair transplantation surgery typically involves moving hairs from the back of the head to the front. This is particularly difficult in women because they usually don't have enough back-of-the head hair to transplant, Christiano said. The technique is also not normally done in men with early-stage baldness because their hairlines are still receding.

Unlike traditional hair transplant techniques, the method described in the PNAS study could potentially grow new hair follicles in hair-loss patients using the person's own cells. It hasn't been tried on a person's head yet, but it has resulted in the generation of human hair follicles on the backs of mice.

People who suffer hair loss and have a limited number of hair follicles could also benefit, Christiano said. That includes people with hair loss that occurs because of burns, scarring alopecia or female-pattern hair loss. The new research could help compensate for this deficit.

This is early-stage research, but Christiano envisions clinical trials in humans could begin in three to five years.

If it were available for human hair restoration, Christiano said the cost would be hard to estimate; she doesn't know how expensive preparing the cells and other parts of the procedure would be for humans. Currently, though, hair transplantation is in the $8,000 to $12,000 range, she said.

How it works

There are specialized stem cells that are found at the base of the hair follicle called dermal papillae. Scientists have shown in previous studies that intact dermal papilla cells can generate hair follicles under skin that doesn't have hair, but not when scientists try to culture them and expand the number of cells.

"You can grow millions of them, but it doesn’t do much good because they can’t instruct the overlying skin to grow hair anymore," Christiano said.

The challenge in this research field has been to find a way to encourage these cells to remember they came from a hair follicle, and regain the signals that induce hair growth.

Christiano and colleagues employed a method of culturing cells called the "hanging drop culture," in which they put dermal papillae cells into drops of tissue culture media on the inside lid of a petri dish. The result was tiny three-dimensional spheres, each containing about 3,000 cells, hanging from the top of the lid.

Researchers then took these spheres and implanted them between the epidermis and dermis of human skin to see if the stem cell spheres could reprogram the epidermis. For the human skin they used infant foreskin because it doesn't normally have hair on it

Finally, they grafted the human skin with the spheres implanted onto the backs of mice.

This technique worked in five out of seven tries, each representing skin cells from a different person, with new hair follicles forming after six weeks. These new hair follicles genetically matched the people they came from, showing they were human - and not rodent - hairs.

What's more, the researchers found that 22% of genes that would be functioning in the cells were turned on in the spheres. Christiano and colleagues had anticipated more than that - this is an area to explore in the future.

Challenges ahead

There are still some other key issues to resolve here such as: Do the new hairs cycle? In other words, if you pluck the newly grown hairs out, will they come back in?

Also, it's not clear yet how pigmentation of hair happens - most of the hairs grown in this experiment were white.

"If someone had a full head of brown hair, and we used this to grow new hair, we wouldn’t want the whole new patch of hair to be white," Christiano explained.

Researchers will also have to make sure that the hair grows at a 30-degree angle like normal human hair, so that it doesn't stick straight out of the head.

Another important hair restoration discovery was made almost 50 years ago with mice: In 1967 a few years after the first working laser was invented, Endre Mester in Semmelweis University in Budapest, Hungary experimented with the effects of lasers on skin cancer. While applying lasers to the backs of shaven mice, he noticed that the shaved hair grew back more quickly on the treated group than the untreated group.

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